Everything connected to the internet needs an address so data is sent to the right place. From the earliest days of the net, addresses have been pulled from the IPv4 pool which has about four billion numbers available.

The rapid growth of the net is close to exhausting this pool. Overcoming the shortage involves shifting to IPv6 which has an almost unlimited pool of numbers to call on.

Despite the shortage, relatively few ISPs have swapped their users to a network built around IPv6.

In a blogpost explaining the move, Jason Livingood from Comcast said it had been carrying out technical trials of IPv6 for over a year.

He said Comcast had taken the step in a bid to overcome the "chicken and egg" situation of there not being much cheap IPv6 hardware available because IPv6 compliant websites and services were scant.